Friday Rock Blogging: Gnammas

A gnamma in Yosemite National ParkGnamma is derived from a Western Australian aboriginal* term for a hole in rock, particularly one which is full of water. The one shown here is from Yosemite again, but unlike so many other features in that park, this gnamma wasn’t formed by glaciers. Instead, it is a testament to the awesome power of small puddles, which speed up the process of erosion in what is initially a slight depression.

Use of the term seems, from quick Google inspection, to be largely restricted to Australia – which is a pity as I think it’s a fun word. The author of the USGS report from which the photo was taken calls it a “weather pit” but that term hasn’t caught on (the report was published in 1913). I’m not aware of any specific terms for these sorts of holes in common use in the American geological community, other than “pothole” which is quite generic, but of course this isn’t my area of expertise so perhaps some gentle reader can set me straight on this point.

*The internet isn’t telling which language specifically, sorry.


  1. Modulator wrote:

    Friday Ark
    Cats, Dogs, Spiders and ? every Friday. We’ll post links to sites that have Friday (plus or minus a few days) photos of their chosen animals as I see them (photoshops at our discretion and humans only in supporting roles). Leave a comment or trackback…

  2. Sunidesus wrote:

    You’re right, that is a fun word! I’m gonna have to try to remember it from now on.
    And now I’ll wander off to explore the rest of the Friday Ark!

  3. ex-rock doctor wrote:

    Gnamma may have been named by the Western Desert indigenous people of Western Australia; see below…
    “Review of how indigenous people managed for water in desert regions of Australia”
    P.S. you’re stepping on the toes of geomorphologists !! Keep up the interesting blog…

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